Common thermosetting phenol formaldehyde type system binders are generally provided as water soluble or water dispersable compositions, which are intended to be easily blended with other ingredients, and which are diluted to low concentrations. It is the diluted compositions which are contacted with such fibers as those employed in engineered, shaped or molded glass fiber products and so forth in order to bind them so in their manufacture.
In such manufacture, the amount of binder employed is in general the amount necessary to lock each fiber into the mass by bonding the fibers where they cross or overlap. For this reason, the binder composition should have good flow characteristics so that it can be applied at a low volume which will flow to mat fiber intersections. The binder composition should be able to be readily thermally cured during normal production cycles. It should be relatively stable for periods of time long enough to permit mixing and application at temperatures ordinarily encountered in fiberizing plants, and the composition should be so dilutable that it permits variations in concentrations for different end products. The cured binder product should provide a strong bond to give sufficient strength and stiffness to the product.
A binder composition much desired is one that can withstand service temperatures of 700.degree. F. to 900.degree. F. A particulary troublesome aspect of binders prepared from a phenol formaldehyde resin system is that such binders exhibit a propensity toward punking when subjected to temperatures in excess of 600.degree. F., which are within the range of temperatures that may be encountered in certain uses.
In the past, a variety of approaches have been taken in an effort to formulate high temperature binder compositions using phenolic resins as the primary binder ingredient. Modification of the phenolic by the addition of nitrogenous modifiers such as dicyandiamide is disclosed by Stalego in U.S. Pat. No. 3,223,668 (Dec. 14, 1965). Borates of various sorts as additives to the binder compositions have been tried. See, e.g., Stalego, U.S. Pat. Nos. 2,931,738 (Apr. 5, 1960) and 3,002,857 (Oct. 3, 1961); Tiede, U.S. Pat. No. 3,253,948 (May 31, 1966), and Foley et al., U.S. Pat. No. 3,839,236 (Oct. 1, 1974).
Urea has been used in the past in phenolic resin binders, especially for its non-punking properties. See e.g., Barth et al., Pat. No. 3,072,595 (Jan. 8, 1963). However, the presence of urea in such binding compositions typically results in a marked lack of stability during low temperature storage of the binder. Binders containing urea are often prone to undergo irreversible phase separation. This separation may also occur in as few as five or six hours, at room temperature, and hence, typical binders containing urea or urea resins can be difficult to use from a processing standpoint.
Walisser in U.S. patent application Ser. No. 875,536 filed June 18, 1986, now U.S. Pat. No. 4,787,108 describes a water soluble phenolic resole-urea composition. That invention, commonly assigned herewith, provides a water soluble, cold storage stable composition made from a phenolic resole that is reacted with urea under acidic conditions and is next neutralized, which retains its good solubility and inhibition to tetra dimer (tetramethylol-4,4'-dihydroxydipehnylmethane) crystallization during cold storage at a temperature from 0.degree. C. to 15.degree. C.
Resole urea binders are typically more soft than resole binders without urea in their cured state. As such, resole urea binders are more particularly suited to low density, resilient thermal insulation end uses as opposed to high density rigid molded or shaped glass fiber containing product end uses where a hard binder is required.
Known resole-alkoxylated melamine binders have been used for the preparation of punk resistant glass fiber products because of the good water miscibility accorded such derivatized (alkoxylated) melamine formaldehyde resins/resole resin mixtures. However, such known alkoxylated melamine formaldehyde/resoles are still prone to lose water tolerance. Known underivatized melamine formaldehyde compositions and especially mixtures of these with resoles are generally unusable because they have very poor water miscibility as exhibited by the turbid solutions that form when such underivatized resins or mixtures are diluted with less than 5 parts water. Good miscibility or solubility in a minimum of 20 parts water is a standard industrial requirement of glass fiber binding resins.
Resoles containing methoxymethyl aminotriazines or methoxymethyl melamines are described by Higginbottom in Canadian Pat. Nos. 1,026,882 (Feb. 21, 1978) and 1,049,172 (Feb. 20, 1979). These patents especially recognize the characteristic of inhibition of tetra dimer crystallization at low temperatures from addition of ceiling additives. However, such products are usable typically only in emulsifiable form, and they may not be commercially viable.
Further, known melamine-containing compositions generally must be stabilized before use with resoles and/or with alcohols, diols and/or triols, and so forth. This is done primarily to provide water miscibility.
For these and other known reasons, resole and melamine compositions that are fully soluble in water, storage stable, yet fast setting and curing, and low in free phenol and free formaldehyde content, and hard when cured, are desirable. There further exists a need for such a single aqueous phenolic resole and melamine system as one which contains all the necessary antipunk ingredients to confer oxidation and thermal stability upon a bindable material, for example, a glass fiber or mineral fiber matrix, prepared therewith, which can be handled like a conventional liquid resole upon application to the bindable material. A fully water soluble, storage stable melamine-containing resole composition should be blendable with water without phase separation or formation of gummy deposits which might clog pumps, pipes and spray nozzles, and it might well be blendable with other suitable resoles. Further, such a resole and melamine composition low in free phenol and free formaldehyde content should thus release a minimal quantity of pollutants to the atmosphere and work areas. Also, fast setting and curing properties, and ability to provide structurally sound C-stage products, would enhance utility and commercial value significantly. Heretofore, the known art has lacked such compositions, and accordingly, the art has further lacked procedures for preparing and using same.